1. Technical Field
This invention relates generally to delivery catheters or sheaths for providing vascular access, and more particularly, to large diameter flexible, kink-resistant introducer catheters or sheaths.
2. Background Information
Introducer sheaths are widely used as conduits to provide percutaneous access to the vascular system. Such sheaths, generally of thin-wall, small diameter construction, have a tendency to kink when traversing within the narrow confines of the vascular system. Increasing the thickness of the sheath wall minimally improves the level of kink resistance, however this level is still considered unacceptable. In addition, increasing the thickness of the sheath wall is undesirable, since it necessitates the use of a larger entry hole.
Sheaths used in certain medical procedures, such as hemofiltration and dialysis, are particularly prone to kinking, since such sheaths remain positioned in a patient's body for an extended period of time. While positioned in a patient, the sheath may be bent or pinched off and, as a result, kink due to repeated use or patient movement. A kinked sheath is unusable and cannot be straightened while positioned in the body of a patient. Consequently, the sheath must be removed, leaving an enlarged, bleeding opening which typically cannot be reused. Vascular access must then be attempted at an alternative site, and the procedure is restarted. Restarting the procedure causes a time delay, which is inconvenient, and at times may be life threatening. In addition, in some cases, an acceptable alternative site may not be available for introducing another sheath.
In addition to their use in introducing and/or withdrawing fluids from the vascular system, introducer sheaths are also utilized for delivering implantable medical devices to a deployment site well within the vascular system of a patient. Although such use of delivery catheters or sheaths is known, particular problems have been encountered when utilizing large diameter catheters or sheaths to implant medical devices. For example, large diameter catheters or sheaths are susceptible to kinking, particularly when the implantable medical device or pusher does not have a uniform diameter to reinforce the delivery catheter or sheath along its entire length. The possibility of kinking is increased when the physician exerts pressure to push the delivery catheter or sheath through an area of thrombus or calcification in the vascular system.
It is desired to provide a large diameter catheter or sheath that is less prone to kinking than existing catheters or sheaths. It is further desired to provide such a device that may be readily tracked as it is manipulated through the vascular system.